Frame grid



Dec. 15, 1964 A, J. ROBINSON, JR 3,161,799

FRAME GRID Filed April 20, 1961 INVENTOR Arch/bald J Rabi/75m, Jr:

TORNE United States Patent 3,161,799 FRAME GRID Archibald J. Robinson, Jr., Emporium, Pa., assignor to Sylvania Electric Products Inc., a corporation of Delaware Filed Apr. 20, 1961, Ser. No. 104,404 6 Claims. (Cl. 313-350) This invention relates generally to electrodes for electron tubes and more specifically to electron tube grid electrodes of the rigid frame type.

In one form of frame grid construction the frame cross supports are formed integrally with the side members. In another form of frame grid construction the frame side members are held in spaced relationship by cross straps attached at the upper and lower edges of the grid window through which cathode emission flows.

This invention may be used with either type of grid frame. In its broad aspects the concept may be used with any grid =using side members held in fixed space relationship by spacing members.

For simplicity in disclosing the invention, the second above-mentioned form of grid frame will be illustrated. In the art such a frame is known as a strap frame, taking its name from the cross straps which space the side members and hold the lateral grid spiral tautly in position across the grid window.

Inter-electrode dimensions or spacings are relatively critical in electron tubes having high amplification factors. This is particularly true of the spacing between the cathode emitting surface and the control grid laterals.

Cathode to grid spacing in a strap frame type of grid is determined by the minor diameter of the grid, i.e., the internal spacing between the front and back grid laterals. In prior art strap frame grid structures, in order to obtain a grid having a given minor diameter, it was necessary to select side members having a thickness equal to said given diameter. Thus when the grid minor diameter was changed, it was necessary to select side members of a different thickness or diameter. Further, it was necessary to change aperture sizes in the two electrode support ing micas, wherein each end of each side member must be tightly mounted.

It is an object of this invention to realize a plurality of grid minor diameters with a single side member thickness and without change in mica aperture dimensions. Otherwise stated, it is an object of this invention to provide simple means whereby side rods of constant end thickness or diameters may be employed regardless of the minor diameter of the final grid, whereby the same insulating spacers may be used for various minor diameters of grids.

Considering one aspect of the invention briefly, grids of varying grid minor diameter are realized by forming or flattening the side rod members adjacent the grid window to the desired grid minor thickness without change in size of the side member end portions.

For a better understanding of my invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following disclosure and appended claims in connection with the accompanying drawings in which:

FIG. 1 is a perspective view of an electrode spacer; and

FIG. 2 is a perspective view of a frame grid with parts broken away; and

FIG. 3 is a perspective view of a portion of a frame grid of modified form.

Referring to the drawings in greater detail, in FIG. 1 there is shown an insulating or mica spacer 10, formed to provide a central aperture 12 of a size to receive the "ice cathode sleeve, two grid frame receiving apertures 14 and other apertures as at and 22 to receive other electrodes or electrode supports.

In FIG. 2 there is shown a grid frame 18 which has been cut in two portions for purposes of illustration only. Grid frame 18 comprises side members 23 and 24, each having like diameter ends 30 and 32 which are formed to fit snugly within mica apertures 14 of upper and lower mica spacers 10, as shown in FIG. 1. Side members 23 and 24 are bridged and held in spaced relationship by cross straps 36 and 38, which may be welded or otherwise fastened to the flattened or formed portion 34 of side members 23, 24.

Also fastened to side members 23, 24 are grid laterals 40. These grid laterals may be formed by spirally winding wire about the window portion 34 of side members thereto at each end. Regardless of how the grid laterals are formed or positioned on the side members, the spacing of the laterals from the cathode emitting surface is determined by the thickness of the grid window portion of the side members, i.e., the greatest dimension between the forward face 42 and the opposite face 44 of each side member 23 and 24. This dimension, which is the grid minor diameter, is shown in FIG. 1 by dotted lines 41. By forming or varying the thickness of the window or intermediate portion 34 of the side members 23, 24, the grid minor diameter may be varied at will without changing either the size of mica apertures 14 or the diameter or thickness of side member ends 30, 32. It is to be noted that the ends of the frame side members may be rectangular or any other desired shape so long as the shape is not too intricate to make a mica or insulating spacer receiving aperture feasible.

Thus, once the shape and size of the end portions of the side members are determined, it is possible to determine the size and shape of apertures 14 in upper and lower mica spacers 10. Then within a reasonable range it is possible to vary the grid minor diameter by changing the thickness of window portion 34 of side members 23 and 24.

Compared to the prior art practice of changing the complete side member size there is a considerable saving in die costs for making insulating spacers, since only one size aperture need be punched for a given range of grid minors. Likewise, only one size side member need be utilized for the same range of grid minors.

Flattening or forming the intermediate or window portions 34 of side members 23 and 24 not only makes it possible to control the grid minor diameter but it also acts to strengthen the side members. Thus the allowable tolerances of the grid minor can be held to smaller variations than would be realized in grids fabricated from side members selected from unformed drawn wire. Further, though most grids of the strap frame type are presently fabricated from molybdenum, my concept makes it possible to use less expensive and weaker stainless steel due to the increased strength realized when the window portion 34 of side members 23 and 24 are formed or flattened.

Referring to FIG. 3 it can be seen that the cross straps 36', 38' also may be attached to the unformed portions of side members 23, 24. There may be an advantage in this construction where cross straps 36 and 38' are welded into position.

vention, it will be obvious to those skilled in the art that various changes and modifications may be made therein 3 without departing from the invention as defined by the appended claims.

Having thus described my invention, I claim:

1. A frame grid comprising a pair of sol-id side members bridged by cross straps and grid laterals secured to the'side members,-said side members each comprising top and bottom like-diametered rounded ends for insertion within insulating spacers and intermediate flat portions of equalthickness and each having substantially parallel faces engaged by the grid laterals.

2. A frame-grid comprising a pair of solid side members bridged by cross straps, each of said side members having rounded like-diametered ends and intermediate flattened portions with the flattened portions having opposed parallel faces and of equal thickness, and a grid wire wound spirally about the flattened portions of the side members With the strands of the wire in engagement with the parallel faces.

3. The structure of claim '1 wherein the cross straps are secured to the flattened portions of the side rods.

4. The structure of claim 1 wherein the cross straps are secured to the round'portions of the side rods.

5. A frame grid comprising a pair of solid side members, having end-portions and an intermediate portion, said end portions being of a given width and a given thickness and said intermediate portions being of a Width greater thansaid given width and of a thickness less than said given thickness, cross straps for holding said side members in spaced relationship, and a helix of grid w-ire wound tightly around the intermediate portion of said side membersto form grid laterals with a grid minor diameter equal to the thickness of the intermediate portion of the side members.

6. A frame grid comprising a pair of solid side members bridged by cross straps and grid laterals secured to the side members, said side members each comprising like shaped and sized ends for insertion within like shaped and sized openings within insulating spacers and intermediate rectangular in cross section flat port-ions of equal thickness and each having substantially flat-parallel faces engaged by the grid laterals, said intermediate portions being smaller in thickness than said ends in a direction perpendicular to the plane of said grid laterals.

References Cited in the file of this patent UNITED STATES PATENTS 1,444,438 White Feb. 6, 1923 1,465,381 Trimble Aug. 21,1923

1,570,265 Lebbink Ian. 19, 1926 2,862,136 Miller Nov. 25, 1958 2,910,609 Millis OCl.27, 1959 FOREIGN PATENTS 1,041,605 Germany Oct.23, 1958 

6. A FRAME GRID COMPRISING A PAIR OF SOLID SIDE MEMBERS BRIDGED BY CROSS STRAPS AND GRID LATERALS SECURED TO THE SIDE MEMBERS, SAID SIDE MEMBERS EACH COMPRISING LIKE SHAPED AND SIZED ENDS FOR INSERTION WITHIN LIKE SHAPED AND SIZED OPENINGS WITHIN INSULATING SPACERS AND INTERMEDIATE RECTANGULAR IN CROSS SECTION FLAT PORTIONS OF EQUAL THICKNESS AND EACH HAVING SUBSTANTIALLY FLAT PARALLEL FACES ENGAGED BY THE GRID LATERALS, SAID INTERMEDIATE PORTIONS BEING SMALLER IN THICKNESS THAN SAID ENDS IN A DIRECTION PERPENDICULAR TO THE PLANE OF SAID GRID LATERALS. 